Unveiled: Researchers reveal pioneering Solar Impulse prototype

Developers in Switzerland have formally unveiled the prototype 'Solar Impulse' experimental solar-powered aircraft which eventually will attempt a round-the-world non-stop flight.

The four-engined aircraft, which has a 63.4m (208ft) wing span but weighs just 1,600kg, was revealed at a ceremony at Dubendorf Airfield today, six years after work began on the programme.

Among the aims of the aircraft - which draws its power from 11,628 silicon cells - is to perform a 36hr endurance flight, including night-flying, before the team embarks on more ambitious tasks.

A second aircraft is planned for 2011 - which, unlike the first, will have a pressurised cockpit - as the researchers bid to make crossings of the USA and the Atlantic, and eventually try to circumnavigate the globe.

Speaking during the unveiling today, aviation pioneer Bertrand Piccard, one of the project's directors, said: "Yesterday it was a dream. Today it's an aeroplane, and tomorrow it will be an ambassador of renewable energies and energy savings - flying day and night with no fuel and no pollution."

Solar Impulse has been guided by Andre Borschberg, who stated today: "Six years ago, when we launched the project, we were facing so many challenges, so many uncertainties, that we could not dare to think of a moment like this one."

Present at the unveiling today was IATA director general Giovanni Bisignani, who described the ceremony as a "great, great event" which "shows to the world that carbon-free flight is possible".